Certain embodiments of the present invention generally relate to connector assemblies and more particularly to an elastomeric connector for electrically connecting flexible circuit boards to printed circuit boards. Other embodiments of the present invention relate to methods of manufacturing an elastomeric connector.
Flexible circuits, or flex circuits, are used with various electronic and electrical devices. In many applications, flex circuits are used in conjunction with rigid circuit boards, such as printed circuit boards. Because flex circuits and rigid circuits are often used together, connectors are used to electrically connect the flex circuits to the rigid circuits.
One way of connecting a flex circuit to a rigid circuit is through an elastomeric connector. Typically, an elastomeric connector includes alternating columns or slices formed of conductive and non-conductive layers, such as formed from silicon rubber. The conductive and non-conductive layers are oriented with ends of each layer engaging conductive parts on the flex circuit and on the rigid circuit. Typically, the elastomeric connector is secured to the flex circuit and the rigid circuit through fasteners such as screws. Through-holes are typically drilled through printed circuit boards to receive the screws. However, the use of screws with an elastomeric connector may preclude the use of the elastomeric connector with various types of electronic equipment. For example, many cell phones today are compact enough to fit in a coat pocket. The use of bulky fasteners, such as screws, typically increases the size of a cell phone. That is, cell phones are designed bigger to accommodate the size of the interior components of the cell phone, where the component size is partially based on the size of connections between components. However, increasing the size of cell phones may discourage consumers from purchasing such phones when smaller, more compact cell phones are available.
As an alternative to screws, some flex circuits are fastened to printed circuit boards through zero insertion force (xe2x80x9cZIFxe2x80x9d) connectors. ZIF connectors are a compressive connector. That is, no screws are used to fasten the components of the ZIF connector, the flex circuit and the printed circuit board together. Rather, the flex circuit is slid inside a ZIF connector that was previously soldered to the printed circuit board. After the flex circuit is slid inside the ZIF connector, the flex circuit, the printed circuit board and the ZIF connector are clamped together. ZIF connectors include small mechanical pins that are used to contact conductive pads on the flex circuit and the printed circuit board. The small pins on the ZIF connector are fragile and may be easily damaged.
ZIF connectors may also cause downtime in the assembly process. For example, if the flex circuit is improperly aligned when the top lid of the ZIF connector is clamped down, a poor connection may result between the flex circuit and the printed circuit board. The poor connection may cause shorting within the system utilizing the flex circuit and the printed circuit board. Additionally, the flex circuit may become dislodged during operation of the system. For example, a flex circuit used within a cell phone may become dislodged if the cell phone is dropped. Some systems include an additional structure that applies pressure on the top of the ZIF connector to decrease the chances of the ZIF connector opening and releasing the flex circuit. The additional force placed on the top of the ZIF connector, however, adds manufacturing time and cost to the system. Additionally, the additional force may damage the small pins of the ZIF connector.
Thus, a need remains for an improved connector and method of connecting a printed circuit board to a flex circuit through an elastomeric connector. Additionally, a need remains for an easier method of manufacturing a connector assembly that uses an elastomeric connector. Further, a need remains for a more robust connector assembly, and for a connector assembly that may be easily changed and upgraded within an electronic or electrical system.
Certain embodiments of the present invention provide a connector assembly for interconnecting a flexible circuit to a circuit board. Additionally, certain embodiments of the present invention provide a connector assembly for interconnecting a flex circuit to another flex circuit or a printed circuit board to another circuit board. The connector assembly includes a circuit board, a base, an elastomeric member, a flex circuit and a cover. The circuit board includes an array of board conductive pads on a first surface of the circuit board. The first surface of the circuit board includes anchoring areas proximate the board conductive pads.
The base includes a bottom surface that is secured to the anchoring areas through tabs on the base. The tabs may be reflow soldered to the anchoring areas. One embodiment of the present invention includes four anchoring areas and four tabs. The base also includes a channel extending through the length of the base. The channel is aligned with and exposes the board conductive pads on the first surface of the circuit board. The base may also include a plurality of ribs located about walls defining the channel. The ribs frictionally engage the elastomeric member to assist in retaining the elastomeric member within the base. The base also includes at least one alignment pin located on the top surface thereof. The flex circuit includes at least one hole for receipt of one alignment pin.
The elastomeric member includes an array of conductive and insulative materials arranged along a longitudinal axis of the member and first and second conductive interfaces electrically communicating with one another. The array of conductive and insulative materials is sandwiched together. The elastomeric member also includes insulative sides formed along opposite sides of the array of conductive and insulative materials in a transverse direction. The elastomeric member substantially conforms to the shape of the channel. The channel receives the elastomeric member. The first conductive interface engages the board conductive pads.
The flex circuit includes a flex first surface having an array of flex conductive pads. The flex first surface is secured to the base such that the flex conductive pads are oriented to align with and contact the second conductive interface. The circuit board and the flex circuit are oriented relative to one another such that the board conductive pads and the flex conductive pads align on top of one another and compressively sandwich the elastomeric member therebetween.
The cover is removably secured to the base. The cover compressively engages a second surface of the flex circuit to bias the flex conductive pads and the board conductive pads against the elastomeric member. The cover may include latches on opposite ends thereof that snapably engage notches formed in opposite ends of the base. The cover and the base cooperate to compress the flex circuit against the elastomeric member.
The connector assembly may be fully assembled through a Z-axis assembly process. That is, each component of the assembly is positioned on top of an adjacent component. The parts of the components do not have to be slid in from a horizontal axis during assembly.
Another embodiment of the present invention provides a method of manufacturing a connector assembly comprising the step of orienting a first circuit having conductive pads at a connector assembly position within a first plane. The method also includes the steps of conveying a connector base along a mounting axis perpendicular to the first plane to a surface mounted position on a first side of the first circuit and conveying an elastomeric member along the mounting axis to a cavity formed in the base in order that a first conductive interface of the elastomeric member electrically engages the first circuit. The method also includes the step of securing a second circuit to the connector base such that the second circuit is in electrical contact with a second conductive interface of the elastomeric member. One of the first and second circuits is a flex circuit. The other circuit is a printed circuit board. The method also includes the step of compressively engaging the elastomeric member and one of the first and second circuits with one another. Further, the cover is conveyed along the mounting axis and snapably engages latches on the cover with notches formed in opposite ends of the base. Tabs on the connector base are soldered to solder pads on one of the first and second circuits.